The invention relates generally to the field of robotics and more particularly to an apparatus for gripping an object between robotic fingers.
Conventionally, wafer handler gripper assemblies comprise a pair of moving assemblies adapted to move between an open and closed position. The moving assemblies may comprise a pair of grippers coupled to extensions or gripper fingers that have end effectors for contacting a wafer (or a similar lightweight substrate). In practice, it is difficult to precisely position the grippers due to play (backlash) in the actuator gears. Precise positioning of the grippers is essential in order to place the end effectors in a repeatable position. End effector position must be tightly toleranced to avoid dropping wafers or damaging wafers by grasping them too tightly.
Accordingly, a need exists for an improved gripper assembly that will precisely position the grippers to place the end effectors in a repeatable position.
The present invention overcomes the problems of the prior art by placing a magnet on each of the moving assemblies so that the attractive force between the magnets moves a portion of the moving assemblies toward each other. Preferably, the magnet is placed on an inner side of each of the grippers. Thus, when the grippers are closed, magnetic attraction between the two magnets mounted on the grippers reduces or eliminates play (backlash) in the gripper assembly by consistently bringing the grippers to a desired position (e.g., as close together as possible).
Other features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.